Slug Sage Mode is another variation of Sage Mode. It is a very powerful version of Sage Mode. It can only be used by Tsunade, Sakura, and Saka. It gives you the ability to sense chakra and enhance any of your jutsu. You also have a slug on your shoulder that can use jutsu to help in a fight.
The only way to obtain this variation of Sage Mode is to go through an incredible amount of training with multiple slugs. Eventually you'll unlock this transformation and will be able to go in and out of this transformation at will. But after you power out of this transformation, you'll be in an extreme amount of pain.